Well if this is your first or hundredth build - - -You should be worried about the strength!
I've been welding for over 40 yrs. - motorcycle frames/gas tanks - car frames/bodies and have even built one off bicycle frames. I've used silicon bronze, sliver braze,brass braze, O/A welding and tig & mig welding. As far as strength goes for a frame, your stick,mig & tig would be your best bet - Braze and O/A welding would be good for body work. But with silicon bronze and brass if your heat is just the slightest bit hot - your strength and flexability has gone out the window, it becomes brittle and can not withstand any stress or vibration. It is best to use some form of filler material that is close to the parent material - ie: steel for steel. - not only will welding heat be a strength factor,but also your ambient temps will factor in as far as expansion and contraction between to dissimilar metals - ie: steel and brass. Plus brass is only a filler rod,not a welding rod, where the parent material and rod are similar and you have penetration.The best thing to do would be to check with your local welding shop or steel distributer for the tensil and shear strength of your parent material and the brass rod.